Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$74.51	5.296%	$78.456	$78.46	$78.45	$78.50
Purchase #2	$181.86	10.250%	$200.5007	$200.50	$200.50	$200.50
Purchase #3	$173.82	6.632%	$185.3477	$185.35	$185.35	$185.30
Purchase #4	$14.46	6.611%	$15.416	$15.42	$15.40	$15.40
Purchase #5	$160.75	4.567%	$168.0915	$168.09	$168.10	$168.10
Purchase #6	$96.46	3.243%	$99.5882	$99.59	$99.60	$99.60
Purchase #7	$35.67	11.765%	$39.8666	$39.87	$39.85	$39.90
7 purchase totals =	$737.53		$787.2667	$787.28	$787.25	$787.30